The lectionary is the book containing the Scripture readings (pericopes) that are appointed to be read in church services according to the cycles of the liturgical year. The lectionary goes back at least to the fourth century, and some of the oldest Greek manuscripts of the New Testament that have survived are Byzantine lectionaries.
The oldest form of the lectionary had the Scripture text with the beginning and ending of each pericope noted in the margin. This is still essentially the format of the Slavic Gospel and Apostol. Contemporary Byzantine lectionaries reflect a further development, in which each pericope is printed in the order in which it is read in the church year. Its beginning is included in the text, and the ending is a clear break.
- Orthodox Christian Scripture Lectionary - An Examination of how the Gospel and Apostolos Lectionary is used throughout the year